The invention relates to a fine-grained product with a grain size of 100% less than 5 mm that is obtained during the production of titanium dioxide in the chloride method in which titanium-containing raw material is reacted with gaseous chlorine in the presence of a carbon-rich substance, preferably coal and/or coke, in a chlorination reactor, preferably with a fluidized bed, to form titanium tetrachloride, the fine-grained product being composed, in the dried state, of
10 to 80% by weight TiO2 
20 to 60% by weight coal and
5 to 20% by weight SiO2.
In the chloride method, titanium ores or xe2x80x9ctitanium slagxe2x80x9d are chlorinated by reacting the titanium-containing raw material with gaseous chlorine in a chlorination reactor while subject to the addition of a carbon-rich substance, in particular coke, for example in a circulating fluidized bed, to form titanium tetrachloride. The liquid thereby formed is freed of all accompanying substances by means of a distillation process so that a very pure starting product is available for the rest of the process. The titanium tetrachloride is then reacted in a burner, while subject to the addition of oxygen, to form titanium dioxide (INORGANIC PIGMENTS, Manufacturing Processes, Noyes Data Corporation, Park Ridge, N.J., USA, 1980, pages 5 to 7).
During this process a portion of the non-reacted titanium-containing raw material/coal and/or coke mixture, which contains as its main constituents
10 to 80% by weight TiO2 
20 to 60% by weight coal and
optionally 5 to 20% by weight SiO2 
with a grain size of 100% less than 5 mm, accumulates in the dust-removal filter.
Since this fine-grained product would impede the carrying out of the further treatment of the titanium tetrachloride, the fine-grained product is removed from the process and dumped or disposed of in another way.
The use of a titanium-containing flux to increase the durability of the refractory brick lining of a furnace is described in DE 4304724 C1. The flux consists of a powdery mixture of residues from TiO2-production and one or more constituents selected from coal, iron, iron oxide or their residues.
In view of the fact that the provision of dumping space or other means of disposal are linked with comparatively high costs and in an effort to supply waste materials for economical utilization, the underlying object of the present application is to present the possibility of making economical use of the fine-grained product described above together with the use of the filter salt (iron sulfate) that results during dilute acid recovery.
The solution to this object consists in using a fine-grained product with a grain size of 100% less than 5mm that is obtained during the production of titanium dioxide in the chloride method in which titanium-containing raw material is reacted with gaseous chlorine in the presence of a carbon-rich substance, preferably coal and/or coke, in a chlorination reactor, preferably with a fluidized bed, to form titanium tetrachloride, the fine-grained product consisting, in the dried state, of the main constituents
10 to 80% by weight TiO2 
20 to 60% by weight coal and
5 to 20% by weight SiO2,
mixed with
20 to 80% by weight filter salt (iron sulfate that is obtained during dilute acid recovery),
0 to 60% by weight residues containing TiO2 from TiO2-production according to the sulfate method,
0 to 20% by weight coal,
0 to 20% by weight sulfate,
0 to 50% by weight ilmenite/TiO2-slag,
with this mixture being treated in a fluidized bed furnace or rotating tubular furnace at temperatures of 900 to 1,300xc2x0 C., as a flux for the purpose of improving the durability of the brick lining of a furnace for the smelting-metallurgical production of metallic materials.
The flux can be present in powder form or in the form of briquettes, pellets or granulated material containing one or more of the binding agents portland cement, blast-furnace cement, aluminous cement, electrostatic-filter ash, bitumen and molasses. The flux can also be used in the form of sinter.
Further coal or coal-containing residues is/are preferably also added to the mixture that already contains coal so that the iron sulfate (filter salt) is reduced to iron oxide.
The invention is explained in greater detail in the following with the aid of an exemplifying embodiment.